During the past decade the sending of documents from one location to another in electronic (soft) form has become ubiquitous. First facsimile (fax) began to replace hard delivery of documents and now E-mail and other forms of electronic transfer are becoming popular. In such electronic transmissions authenticity is becoming more and more of an issue.
At first blush the problem is simply one of not having an "original" signature on the received copy. Thus, systems are being devised to attach an electronic signature which can be authenticated both at the time of reception of the document and at subsequent points in time. Such signatures are necessary for certain document types, particularly when the document is to be used later in a court of law, or before a government official, to prove some contention pertaining to the content of the electronic transmission.
Another problem that exists and that has not been addressed is the fact that because of the speeds and relative ease of electronic transmission several different transmissions may occur in a matter of hours or even minutes, each changing one or more pages of the resultant copy. Traditionally, ambiguities over date are resolved because only one piece of paper could, as a practical matter, physically be delivered bearing a single date. This has all now changed. The same document may now be sent numerous times during the course of a single day and, if desired, different pages can have different content after each transmission. To make matters worse, the same document can be sent from different locations, some far away geographically, all arriving at roughly the same time. In this scenario the issue is not so much authenticity, but rather what document came at what time from which location containing what subject matter.
A need therefor exists in the art of electronic document transfer for establishing a mechanism for later determining the time a transmission was sent, proving where it was sent from, and proving the exact content of the transmission to a high degree of certainty.
Another need exists in the art of electronic document transfer for establishing a mechanism for later determining that a document was not sent at a particular time or that the document did not have a certain content therein.